Printing lenticular film



Dec. 22, 1936. J, EGGERT ETAL 2,064,892

PRINTING LENTICULAR FILM Filed Feb. 27, 1934 2 Sheets-Sheet 1 nvenfors:

By Afforneys 1936- J. EGGERT ET AL 2,054,392

PRINTING LENTICULAR FILM Filed Feb. 27, 1934 I 2 Sheets-Sheet 2 In venfors By Afforneys Patented I Dec. 1936 UNITED STATES PATENT OFFICE to I.G. Farbenindustrle Aktiengesellschaft, Frankfort-on-the-Main, GermanyApplication February '21, 1934, Serial No. 113,137

' In Germany February 28, 1933 2 Claims. ((71. 95-75) Fig. 3 shows theoptical condition during ex- Q posure, 15 Fig. 4 shows the incidence ofthe light on the marginal part of the film on an enlarged scale,

Fig. 5 shows printing the middle of the green filter strip on the middleof the picture field,

Fig. 6 shows printing of another color than go green on the middle ofthe picture field, and

Fig. 7 shows the incidence of the light rays on the marginal part of abent film.

In printing by contact a lenticular film on to another lenticular film,the contact being heas tween the embossed sides of the films, care mustbe taken that a pencil of light projected on the picture field of theoriginal is projected on the marginal portion thereof at another anglethan on the centralportion. For this purpose it has so already beenproposed to use a source of light in co-operation with a slot-likediaphragm and to move this aggregate over the whole picture field inprinting.

According to the present invention which avoids 35 moving of thesource-of light, the original and the film to be printed on are arrangedwith their embossed sides in contact, bent to a cylindrical plane, andexposed from the side of the original. The radius of curvature of thecylindrical plane 40 is determined by the condition that the linesjoining the borders of the films with the center of the source of light,form with the perpendiculars to the tangents to the place at the bordersof the films the same angle as the lnes joining the 45 center of theexposure filter or s virtual image with the perpendiculars erected onthe borders of the film. The extension of the source of light 7 in thedirection of the lenticular elements should be as small as possible,whereas the extension 50 of the source of light in the direction De -Pmdicular to the lenticular elements must be such that the source oflight subtends the same angle at the center of the film as the filter orits virtual image subtended at the center of the original 55 when thatwas being exposed.

The process will now be described with reference to the accompanyingdrawings.

Fig. 1 shows the arrangement and relations of the film and filter duringthe taking of the original film. I is the lenticular film and 2 is theexposure filter arranged at the distance a from the film I. From thepicture middle 3 the filter appears under the angle ,3. The lines drawnfrom the filter middle 6 towards the borders of the picture field I andthe perpendiculars erected on the borders of the pictures form the anglea.

Fig. 2 shows the arrangement and relations of the original film, theprinting film and the source of light in printing. i is the originalfilm which together with the printing fihn 4 is curved to form acylindrical surface. On the concave side of the cylindrical surface isarranged the source of light 5 at any required distance from the film,but in such a breadth that at the picture middle I it subtends the angle5 equal to the angle subtended, during the exposure, by the exposurefilter at the picture middle 3. The curvature of the film is such thatthe lines joining the picture borders with the center 6' of the sourceof light 5 together with the perpendiculars erected on the tangents ofthe picture borders form the angle a which must be equal to the angle aof Fig. 1 if an original exposed under the conditions shown in Fig. l isbeing printed. M is the center of curvature.

Fig. 3 shows the optical conditions during exposure of the originalfilm, as they have been shown in Fig. 1, however the lenticular film hasbeen drawn on an enlarged scale. 2 is the image of the filter whenviewed from the film. 9i0=r is the red filter strip, 89=g is the greenfilter strip, II is the middle of the green filter strip which issimultaneously the middle of the whole filter, and 'I8=b is the bluefilter strip. The

trace of the .rays has been shown for the-lenticular element i2-l3 onthe marginal part of the original film l. The trace of.the rays ischaracterized by the bordering rays llI-I2-l0' and Ill-ll-IO and theaxial ray l0l4i0'.--

are in touch with the air only on one side, has

been disregarded for the sake of clarity. In an analogous mannerprojection of the point I at 1 will be found by tracing the rays'Il2-1', 1-44- 1, 1-43-1". Attention is called to the fact that on themarginal parts of the film the projection of the filter has beendisplaced behind each lenticular element towards the margin withrelation to the axis i4-i5. Thus, in the margin opposite to that justconsidered, projection of the points 1 and ID at 'l and ill" isdisplaced towards the margin.

In Fig. 3 the mutual dimensions of filter and film are not thosecorresponding with the actual relations, because for the sake of claritythe lenticular elements have been drawn on too great a scale incomparison with the filter and its distance, and the breadth of thefilm. Thereibre, the pencil of rays limited by the rays l0-l2 and ill-l3appears to be convergent. In reality these rays are practically parallelinview of the small dimensions of the lenticular elements (about 0.03mm. when the apparent distance of the filter is, for instance, 40 mm.).These relations are more correctly represented in Fig. 4; all the raysstrik ing the lenticular elements and emanating from the same point iiiof the filter are parallel so that the axis iii-ll and their productionagainst 30 is characteristical for the color of these rays. Analogouslythe rays parallel to the axis 'I'-l| are characteristical for the colorof I.

In Fig. 5 there is shown the process of printing the middle of the greenfilter strips on the middle of the picture field. AC, CE and EG arethree lenticular elements of the original. 1' g b are the areas whichcorrespond with the red, the green and the blue filter strip of theexposure filter. M, Ml, M are the middles of the projections of thegreen filter strips confederate with each lenticular element of theoriginal film. 5 is a thread-like source of light which is shown in aposition nearer to the film than in reality, but which emits a pencil oflight with relation to point M1 under the correct angular conditions.These rays diverge from M1 and just fill the lenticular element CE whenreaching the latter. The direction of these rays emanating in parallelcondition is given by the axis MID. The same holds true with regard tothe trace of rays for the lenticular elements AC and EG so that parallelrays emanate from the whole front of the film. Therefore, if alllenticular elements are well formed, it is not possible to detect fromwhich lenticular element a single ray emanates. It is only possible todetermine the direction which, as shown above, is decisive for the colorof the confederate picture point. Therefore, it does not matter, whichis the position of the lenticular elements of the printing film withregard to those of the original film, whether they face exactly thelenticular elements of the original or whether they are displaced withregard to them, as in exposure of the original parallel rays strike theprint which are exactly united under the middle of the lenticularelements since they strike the printing film exactly perpendicularly,that is to say S1, S2. S3, S4 are images of the points M, M1, M2.Attention is drawn to the fact that with the relative position of thelenticular elements of the original and the print as shown in Fig. 5 forinstance, the point M1 has not one image on the print but two, namely S:and S3. These images lie on exactly corresponding places under thelenticular elements and, therefore, yield in projection the same color.

In Fig. 6, it has been shown for the same place of the picture field,that is to say, for the middle, how another color is printed. The middleof the red strips has been chosen for this purpose. 0n consideration ofthe figure it will be seen that the pencil of light emanating from redstrips is only partially projected on the lenticular element CE, namelyon the part CF. The remaining portion falls on the part B0 of thelenticular element AC,

which lies adjacent the lenticular element CE. The further course of therays must be considered separately for these two portions. As in Fig. 4the rays of the pencil of light emanating from the lenticular element CEare parallel with the axial ray 'I'D. Similar considerations areapplicable for the other lenticular elements so that parallel pencils ofrays emanate from the lenticular elements of the original. Theirdirection corresponds with that of TD and is inclined towards the axisof the lenticular elements. Between these pencils there are gaps at acertain distance from the lenticular elements of the original which gapscorrespond with those portions of the pencils that are projected on theadjacent lenticular elements. Like Fig. 5 the pencil of light projectedon the lenticular elements of the printing film is directed to thoseplaces 0! the emulsion layer which correspond with the direction ofincidence of the pencils. Inasmuch as this direction is the same for theprinting film as for the original the point T must be copied in pointsS: and S3. The pencil oi rays projected on the lenticular element ACfrom T emanates from this lenticular element parallel with the axis TB.Similar considerations are applicable to the pencils of rays emanatingfrom the remaining lenticular elements. The pencil is projected on KBand is copied at the place where the parallel to the axis TB through themiddle L of this lenticular element meets the emulsion layer in 81. S1corresponds as to position with relation to UK with that of T withrelation to CE. that is to W T is reproduced in the correct color.

In the described instance the pencil of light which serves forillumination of the original has partly followed another way than thepencil of light in exposing the original. In view of the obliqueincidence of the light rays on the copying lenses there may occurdistortions whereby the rendition of the colors is deteriorated and,therefore, it is advisable to restrict the oblique incidence to as smalla part as possible. This is most important for the lenticular elementspositioned at the margins of the film. As already described above withreference to Fig. 3 the middle of the green filter strip is protected sothat the incidence is oblique whereas the incidence of the other colorsis less but still subaantinlly oblique. Now, in order that the rays ofthe source of light be projected under the same angle on the marginsotthefilmason themiddlepnrtitwouldbe necessarytodisplncethesourceoilighttownrds the margins of the film.

In order to avoid displacement of the source of light the film is bentto such an extent that the rays of the source of light proceed in thedirection of the rays from the middle of thegreenfilterstriponthemnrginsoitbefilmin exposure. In Fig.7 the numberscorrespond with thoseofFlg. 3,howeverinthisl"igure7thefilmhasbeenbent.sothatthesomceoi'lightprojectstheraysonthefilminthesamedinctionssin exposing the original. Thegeometrical rules for fulfilling this condition have been dncribed.

The printing process according to thisinventionhasofcourseminfiuenceonthepositkmandsizeofthepmiectionfilterwithreiationto the projected print. Theserelations correspond with those obtained during exposure of the originalfilm.

What we claim is:

1. A process of printing lenticular him which comprises arranging anoriginal and a printing film in contact with the embossed sides lacingeach other, arranging a source of light with small extension in thedirection parallel to the lenticular elements in front of the originalso that it is seen from the center of the original under the same angleas was seen the multi-color filter in taking, and bending the two filmsto a cylindrical plane so that the angle between the perpendicularserected on the tangents in the borders of the film and the lines fromthe border of the mm to the center of the source of light form the sameangle as these lines form in taking.

2. In an apparatus for printing lenticular film in combination, anoriginal and a printing film in contact, a source of light in front oi!said original having a small extension in the direction parallel to thelenticular elements and in the direction perpendicular to the lenticularelements an extension that it is seen under the same angle as was seenthe multi-color filter in taking, said films forming a cylindrical planeso that the angle between the perpendiculars erected on the tangents inthe borders of the film and the lines from the borders of the films tothe center of the source of light form the same angle as these linesform in taking.

JOHN EGGERT.

GERD HEYMER.

